The influence of host galaxy morphology on Type Ia Supernovae standardization and cosmological analysis

Abstract

Type Ia Supernovae (SNe Ia) are known to be good distance indicators in the Universe. It becomes possible thanks to the empirical relation between SN light curve parameters and luminosity. However, the Hubble diagram still shows some remaining intrinsic dispersion, which can be related to the effect of supernova environment. In this work we study how the host galaxy morphology affects SN Ia standardization and cosmological analysis using 330 supernovae from Pantheon cosmological sample. We reproduce the Pantheon Hubble diagram fit and perform the fit separately for two SN groups according to the morphological type of their host galaxies: early-type and late-type. We found that in passive stellar environment SNe Ia have higher $\alpha$ and smaller $\beta$ standardization parameters than supernovae hosted by late-type galaxies. The early-type galaxies contain brighter supernovae after stretch and colour corrections. Thus, the host morphology correction do affect the Hubble diagram fit. We also noticed that the host mass correction alone was not enough to take the influence of the environment into account. The observed intrinsic scatter in SNe Ia luminosity can still be partially compensated by a more correct consideration of the environmental correction.